This invention relates to processes for the production of free-flowing, non-fibrous, storable nitrocellulose by briefly treating the water- or alcohol-moistened nitrocellulose with a solvent mixture of a solvent for nitrocellulose and a lower aliphatic alcohol, decanting the alcohol-containing liquid phase and processing the nitrocellulose-containing phase into granulate using a screw extruder.
Because it ignites spontaneously when dry, nitrocellulose (NC) has to be treated with a moistening agent, such as a lower alcohol, preferably methanol, ethanol, isopropanol or butanol, in order to reduce the danger of ignition during storage and transport. This alcohol-moist nitro-cellulose is marketed in the form of fibrous wool or as a compact product. In the first case, the low bulk weight results in high freight costs which is not the case with the compact product. However, since the fibrous structure of the wool remains intact during the compaction process, a large amount of dust generally accumulates during processing and handling in commercial circles, further increasing the danger of ignition.
Accordingly, there is a need to make alcohol-moist nitrocellulose available in free-flowing, preferably granulated form.
Known processes are described in DAS 30 41 085, according to which nitrocelluose is dissolved in a solvent mixture of a solvent and non-solvent for nitrocellulose to form a homogeneous, non-tacky phase from which the volatile constituents, such as water and alcohol, are subsequently removed by distillation, optionally after the required forming process. This known process gives a nitrocellulose which is easy to handle and which is particularly suitable for the production of additives for polyurethane lacquers because the compounds reacting with the isocyanate groups, namely water and alcohol, have been completely removed.
U.S. Pat. No. 3,284,253 describes a process for the production of nitrocellulose moistened with a non-solvent. In this process, the nitrocellulose is first softened by the addition of an amount of an organic solvent to an aqueous nitro-cellulose suspension such that the nitrocellulose structure disappears, and then processed into a granulate, the organic solvent being distilled off and the remaining excess water separated off. A volatile non-solvent, preferably toluene, is added to this moist nitrocellulose and the water azeotrope is distilled off so that a free-flowing nitrocellulose moistened with toluene is ultimately obtained.
The disadvantage of these known processes for the production of free-flowing nitrocelluose lie in the elaborate treatments of the nitrocellulose with the non-solvent, particularly the distillation step for removing the non-solvent used in the softening of the nitrocellulose. This process step can be avoided by the process according to the present invention.